From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-04-iad.dyndns.com (mxout-094-iad.mailhop.org [216.146.32.94]) by lists.bufferbloat.net (Postfix) with ESMTP id 373772E015C for ; Fri, 11 Mar 2011 11:05:12 -0800 (PST) Received: from scan-01-iad.mailhop.org (scan-01-iad.local [10.150.0.206]) by mail-04-iad.dyndns.com (Postfix) with ESMTP id 4869D83807D for ; Fri, 11 Mar 2011 19:05:13 +0000 (UTC) X-Spam-Score: -1.0 (-) X-Mail-Handler: MailHop by DynDNS X-Originating-IP: 209.85.213.171 Received: from mail-yx0-f171.google.com (mail-yx0-f171.google.com [209.85.213.171]) by mail-04-iad.dyndns.com (Postfix) with ESMTP id 04F1E838072 for ; Fri, 11 Mar 2011 19:05:12 +0000 (UTC) Received: by yxh35 with SMTP id 35so1562345yxh.16 for ; Fri, 11 Mar 2011 11:05:11 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=gamma; h=domainkey-signature:mime-version:in-reply-to:references:date :message-id:subject:from:to:content-type:content-transfer-encoding; bh=6oHvgMJnHEqYcCdAF5dNLNZ2lxyaRDdOn3gEpyXq44Q=; b=Jn52fz5DzTXpEGySoH1a2vAld1TGCaPjp2QdK2oNDz3Go2fBvqFf8uZDi9vXPQ64Sf oCJlLAEcweLpiQ6iuOyqc5DrfeU099f50eHoq4bsC/NRpXy4X7cO6aHlKvyeSgvD9fjm p4X9MliJDE6Sj3LHsg22Jyf7a2I/otzTHbGFQ= DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :content-type:content-transfer-encoding; b=YuOTP4yrSZZqALeLncXN15Aym3olnAtz2Pp5mhyZTMWMsSU3ey4tuAB2XrGF1n7sgl uPGKyJtd3I7/0qoAKlE4ZLXnN0cuin7i2VAiFfhMCFNtEA4qiBjDPcw8IdU7lViu547J EOnTDSKO4V3RRi34QzYpBdFF5xZUHQ1HgW9Gk= MIME-Version: 1.0 Received: by 10.147.150.9 with SMTP id c9mr14160629yao.7.1299870310496; Fri, 11 Mar 2011 11:05:10 -0800 (PST) Received: by 10.147.99.13 with HTTP; Fri, 11 Mar 2011 11:05:10 -0800 (PST) In-Reply-To: <580BEA5E3B99744AB1F5BFF5E9A3C67D016E72AA15@HE111648.emea1.cds.t-internal.com> References: <580BEA5E3B99744AB1F5BFF5E9A3C67D016E72AA15@HE111648.emea1.cds.t-internal.com> Date: Fri, 11 Mar 2011 14:05:10 -0500 Message-ID: From: Srikanth Sundaresan To: bloat@lists.bufferbloat.net Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Subject: Re: [Bloat] some market observations X-BeenThere: bloat@lists.bufferbloat.net X-Mailman-Version: 2.1.13 Precedence: list List-Id: General list for discussing Bufferbloat List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 11 Mar 2011 19:05:12 -0000 On Fri, Mar 11, 2011 at 8:22 AM, wrote: > interesting discussions going on here.. > > A consumer-oriented magazine complained that a VDSL access rated 50 mbps = only delivered 31 mbps. It turned out that they used a single TCP session f= or their measurements. At those speeds, delay and packet loss determine the= maximum throughput, independent of the available bandwidth. The formula in= RfC 3819, Section 8.5 yielded an estimate of ~32 mbps for the given delay = and loss, which matched nicely the actual measurements. > The same effects can be seen even on smaller pipes. I see about a ~0.5Mbits/s gap between multi-threaded and single threaded measurements in my 3Mbits/s DSL line at home. (Loss ~0.7%) > With increasing access bandwidths, ISPs are forced to look into the delay= issues. > > DSL bit error rates go up when everybody switches to DSL. DSL standard bo= dies look into link layer mechanisms to mitigate this, but all solutions ad= d delay. It's hard to find the right balance between delay and packet loss;= both hurt TCP performance. As delay can't be controlled by a single ISP, t= he temptation is high to focus on the bit errors. > To a very large extent, it can be, as most of the delay is in the local loop. For DSL, it is at least 8ms and can go up to 40-50 ms. It's a significant fraction of end-to-end latency for most popular websites. Error correction techniques make this worse. - Srikanth